The present invention relates in general to medical instrument guidance for minimally invasive medical procedures and, in particular, to three-dimensional guidance using stereo radiolocation and related imaging for penetration path selection. The present invention has particular advantages with respect to sentinel node biopsy procedures.
The use of radioactively tagged materials for medical imaging, tissue identification and certain localization procedures is well-established. One such application relates to identification of a sentinel node in connection with the staging and treatment of breast cancer. Determining whether cancer has spread from a mass within the breast to the lymph nodes, generally located near the patient""s armpit, is important in selecting a course of treatment and establishing a definitive prognosis. In this regard, a radioactively tagged material or radiopharmaceutical may be utilized to assist in locating the sentinel node.
Generally, the radiopharmaceutical is injected near the site of a cancerous mass within the patient""s breast and then drains to the sentinel node. The injection may alternatively be made subdermally or periareolarly. A photon detector such as a hand-held probe can then be used to locate the sentinel node by manually moving the probe over the armpit area while monitoring detector readings to identify a radiation peak. Such probes have been used to guide surgeons to the site of the sentinel node and it has further been proposed to use such probes in connection with certain medical instruments for minimally invasive sentinel node extraction.
While such procedures or proposals represent a significant advance in the diagnosis and treatment of breast cancer, a number of challenges remain with respect to full realization of the associated potential benefits. First, given the gravity of the medical context, accurate identification and localization of the sentinel node is essential to provide physicians with the confidence necessary to rely on such procedures in making diagnoses and establishing courses of treatment. However, because the detector is hand-held, the photon detector may have limited accuracy in localizing the node. In addition, there is no ability to correlate, to the required accuracy, the probe location to the location of any separate instrument used for extraction. Moreover, minimally invasive procedures are hampered by a concern for damaging nerves or other sensitive tissue that is present in the vicinity of the sentinel node during penetration of the medical instrument into the axilla. Accordingly, surgical node removal remains the standard, in part because open surgical removal allows the surgeon to avoid damage to such sensitive tissues.
The present invention is directed to three-dimensional localization of an area of interest within a patient""s body for instrument guidance based on photon/radiation emissions. The invention thus allows for accurate determination of the spatial coordinates of the area of interest identified based on emissions therefrom, for example, as a result of using a radioactive material or radiopharmaceutical. Such coordinates can be used in accordance with the present invention to guide a medical instrument to the identified location, for example, for treatment, sampling or extraction. The invention also provides for spatially correlated imaging to facilitate penetrate path selection. Moreover, the invention enables flexible positioning of one or more photon detectors, imaging probes, and medical instruments while maintaining identifiable positions relative to a known frame of reference so as to facilitate localization and targeting of difficult to access areas of interest, as well as penetration path selection.
In accordance with one aspect of the present invention, the spatial location of an area of interest within a patient""s body is identified relative to a predetermined frame of reference by radiolocalization. An associated apparatus includes: a patient support for supporting the patient in a substantially fixed position relative to a predetermined frame of reference; a photon detector system for receiving photon emissions from an area of interest within the patient""s body and providing location information based on the emissions; and a processor for identifying the three-dimensional spatial location of the area of interest relative to the predetermined frame of reference based on the location information from the photon detector system.
It will be appreciated that identifying the location of the area of interest relative to a predetermined reference or concurrent frame facilitates subsequent or concurrent medical instrument targeting, imaging or other procedures. In one embodiment, a multiple pin hole collimator is used in conjunction with a single gamma camera to generate the location information so as to provide three-dimensional data. Alternatively, two or more detectors may be used for stereo radiolocation based on gamma radiation, visible light, near infrared or infrared photon emissions. In the latter case, the photon detector system may include a first photon detector, mounted in known spatial relationship and moveable with respect to the predetermined frame of reference, for providing first information regarding the position of an area of interest within the patient""s body based on photons emitted from the area of interest; and a second photon detector, mounted in known spatial relation and movable with respect to the predetermined frame of reference, for providing second information regarding the position of the area of interest within the patient""s body based on photons emitted from the area of interest. In this latter case, it will be appreciated that each of the photon detectors can provide directional information regarding the area of interest based on radiation propagating from the area of interest. Thus, in this case, by using two photon detectors that provide spatially correlated information, three-dimensional coordinates can be determined regarding the location of interest thereby facilitating localization, e.g., for instrument guidance.
In accordance with another aspect of the present invention, a medical instrument is guided to an area of interest within the patient""s body based on radiolocation. An associated apparatus comprises: a patient support for supporting a patient in a substantially fixed position relative to a predetermined frame of reference; at least one photon detector, mounted in known spatial relation and movable relative to said predetermined frame of reference, for providing position information regarding the area of interest based on photons emitted therefrom; a medical instrument support, located in predetermined spatial relation and movable and relative to said predetermined frame of reference, for use in targeting a medical instrument at the area of interest; and a processor for receiving first information regarding the location of the area of interest, receiving second information regarding a position of the medical instrument and providing guidance information for use in targeting the medical instrument at the area of interest. By mounting the medical instrument support and the photon detector(s) in a spatially correlated manner relative to the patient support, radiolocalization information can be used for targeting a medical instrument to a location of interest within the patient""s body.
According to a still further aspect of the present invention, a substantially real-time imaging system is used in connection with a radiolocalization device for selection of a penetration path for targeting an area of interest with a patient""s body. The radiolocalization device is utilized to determine the spatial location of the area of interest with the patient""s body relative to a predetermined frame of reference. The real-time imaging system includes an imaging element that is mounted in known spatial relation and movable relative to the predetermined frame of reference for providing real-time images that can be used for penetration path selection. Preferably, a curser or other marker indicating the calculated location of the source of radio emissions is superimposed on a display of the real-time imaging system to identify the area of interest. A physician can then use the real-time images to select a penetration path to the identified area of interest while avoiding sensitive tissues that may be interposed between the skin of the patient and the area of interest. Real-time imaging also provides a confirmation to the physician that the calculated source of radio emissions coincides with the area of interest displayed by the real-time imaging system. The object targeted by the radio labeled agent is likely visible by the type of real time imaging system selected.
According to a still further aspect of the present invention, a support assembly, positionable in three-dimensional space, is used to facilitate radiation based instrument guidance. The flexible positioning system, in one implementation, is used in connection with a medical instrument guidance device that includes: a support for supporting a patient in known spatial relation relative to a predetermined frame of reference; one or more photon detectors, mounted in known spatial relation and movable relative to the predetermined frame of reference, for identifying a position of the area of interest based on the photons emitted therefrom; a medical instrument support, mounted in known spatial relation and movable relative to the predetermined frame of reference, for supporting a medical instrument for use in penetrating to the area of interest; and an imaging element, mounted in known spatial relation to and movable relative to the predetermined frame of reference, for providing imaging that can be used for penetration path selection. One or more of the photon detector, medical instrument support, and imaging element may be supported using the flexible positioning system in accordance with this aspect the invention.
The flexible positioning system includes a support for supporting a detector, imaging element or medical instrument as noted above. The system further includes a first positioning mechanism for allowing movement of the support in three spatial dimensions and a second positioning mechanism for allowing angular positioning of the support. Preferably, the second mechanism allows for angular positioning relative to two transverse reference planes. The system further includes a subsystem for tracking the spatial and angular position of the support. The spatial position and angular position may be tracked using encoders, magnetic field devices, radio frequency (RF) transmitters and antennae/receivers or other appropriate means. Alternatively, where the support supports an imaging element, feedback regarding the targeting position may be obtained based on the imaging information received from the imaging element. The flexible positioning element thereby facilitates targeting of a medical instrument in difficult to access areas such as an armpit region of a patient, e.g., for sentinel node identification and targeting, and facilitates penetration path selection. This element also allows for penetration path selection in relation to penetrating the abdomen of a patient in such a manner as to minimize injury to the patient""s vascular, lymphatic and nervous systems as well as vital patient organs.